Former central bank Governor Stepan Kubiv, the president's representative in parliament, will be first deputy prime minister and economy minister.

The defense and foreign ministers, who are both appointed by the president, retain their positions.

EU foreign-policy chief Federica Mogherini called the new government's appointment "a crucial development at a time when new momentum in the country is badly needed."

"The European Union remains committed to supporting Ukraine politically and through financial and technical assistance in its efforts to implement key reforms, modernize the country, and fight corruption," she added.

"The momentum offered with the appointment of the new prime minister and government must be seized now," Mogherini said.

The White House said U.S. Vice President Joe Biden congratulated Hroysman in a telephone call and urged the new premier and his team to "move forward quickly" with reforms in order to maintain international support for the government in Kyiv.

These include fulfilling Ukraine's International Monetary Fund (IMF) commitments, implementing the Minsk agreements aimed at regulating the conflict with Russia-backed separatists in eastern Ukraine, and confirming a new "reformist" prosecuto-general, the White House said in a statement.

Ukraine's economy and currency have been pummeled over the past two years as the country grapples with rampant corruption and its military battles Moscow-backed separatists in its east.

German Foreign Minister Frank-Walter Steinmeier welcomed Hroysman's appointment as a "chance to end the phase of political uncertainty in Kyiv." He also urged Ukraine to speed up the pace of reform, saying that Ukraine "has no time to lose."

Speaking during an annual televised question-and-answer session, Russian President Vladimir Putin expressed hope that the new Ukrainian cabinet will “act pragmatically, in the interests of the people, their own people, without being guided by some phobias or trying to please some foreign structures."

Yatsenyuk submitted his resignation earlier this week after weeks of pressure for him to step down.

His cabinet survived a no-confidence vote in February, but two parties left the governing coalition to protest the failure to oust the prime minister, who was under fire over the worsening economy and slow pace of Western-backed reforms.

The political crisis threatened to trigger early elections and jeopardized the flow of billions of dollars in international financing.

Yatsenyuk had been in office since former Russia-friendly President Viktor Yanukovych was ousted by protesters angry in February 2014 over his decision to abandon plans for a landmark pact with the EU, and instead forge closer ties with Moscow.

Yanukovych's downfall was followed by Russia's illegal annexation of Crimea in March 2014 and a drawn-out conflict with Moscow-backed separatists in eastern Ukraine that continues to dominate Ukraine's economic and political life.

"I understand the threats we are facing. I would like to highlight three of them: corruption, poor governance, and, dear colleagues, populism, which is as big a threat to our country as the enemy in the east," Hroysman said on April 14.

Calling his nominee "a politician of a new generation," President Poroshenko told parliament that the next government would "pursue a relentless course toward European integration."

He also said fighting corruption was crucial to improving the investment climate in Ukraine.

Poroshenko said on April 10 that $1 billion in U.S. loan guarantees would be approved once the new government was formed. More aid would follow, he added, including 600 million euros ($680 million) from the European Union and $1.7 billion from the International Monetary Fund.

Hroysman was thrust onto the national scene after the Euromaidan unrest that toppled Yanukovych.

He has been parliament speaker since November 2014 and previously served as a deputy prime minister under Yatsenyuk.